A recent significant advancement in the field of gas dynamics is the development of coherent jet technology which produces a laser-like jet of gas which can travel a long distance while still retaining substantially all of its initial velocity and with very little increase to its jet diameter. One very important commercial use of coherent jet technology is for the introduction of gas into liquid, such as molten metal, whereby the gas injector may be spaced a large distance from the surface of the liquid, enabling safer operation as well as more efficient operation because much more of the gas penetrates into the liquid than is possible with conventional practice where much of the gas deflects off the surface of the liquid and does not enter the liquid.
In some circumstances it is desirable to change the length of the coherent jet, such as its length from the gas injector to the liquid surface. This can be done by changing the elevation of the gas injector, i.e. bringing it closer to or farther from the surface of the liquid, but this is cumbersome and time consuming. It is also possible to change the length of the coherent jet by changing the dimensions of the gas injector nozzle but, again, this is inconvenient. Furthermore, it is possible to change the length of the coherent jet by changing the flowrate of the gas which comprises the coherent jet. However, such practice may be undesirable because it can potentially adversely affect the overall process, e.g. metal refining, wherein the coherent jet technology is being employed.
Accordingly it is an object of this invention to provide a method for changing the length of a coherent jet without the need for changing the equipment used to produce the coherent: jet, and also without the need for changing any other aspect, such as the flowrate, of the gas making up the coherent jet.